1. Field of the Invention
The present invention relates to a fastening device for use on a pipe shaft and a hollow square shaft for use in a business machine and other industrial machines.
2. Description of the Prior Art
It has been the practice to use a solid shaft 2, as shown in FIG. 12, for a paper feed shaft of a business machine and other industrial machines.
A snap ring groove 2a for receiving a snap ring for positioning an element on the shaft can be peripherally formed around the circumference of the solid shaft 2, and a stop 3 can be fitted into the snap ring groove 2a in order to secure the desired elements such as gears and rollers thereon.
It has been proposed in such a business machine and other industrial machines to use a pipe shaft 4, as shown in FIG. 13, in order to decrease the weight or to save material. The wall thickness of the pipe shaft 4, however, is so thin that it is difficult to form a snap ring groove 4a, into which a ring 5 can be fitted.
In order to overcome the aforementioned disadvantages, the pipe shaft 4 is subjected to cold working to form an upset portion for forming a snap ring groove 4a.
But work hardening is likely to occur in the snap ring groove 4a which is characteristic in chrome steel, cracks are sometimes caused, and there is danger of bringing about a cutting of the metal fibers, so that the pipe shaft may break after a period of use.
In addition, when a displacement force is given to the parts such as rollers, they are likely to be moved or shaken.
Although a bearing for securing the parts may be easily provided at an end portion of a hollow square shaft, it is extremely difficult to mount a bearing at the middle portion of such a hollow square shaft.